1. Field of the Invention
The present invention relates to a solid-state image pickup device, a method for manufacturing the solid-state image pickup device, and a camera. In particular, the present invention relates to a solid-state image pickup device, in which pixels having diodes are arranged in a matrix on a light-receiving surface, the method for manufacturing the solid-state image pickup device, and a camera provided with the solid-state image pickup device.
2. Description of the Related Art
For example, in the configuration of a solid-state image pickup device, e.g., a CMOS sensor or a CCD element, light is allowed to enter photodiodes (photoelectric conversion portion) disposed on a surface of a semiconductor substrate, and an image signal is obtained on the basis of signal charges generated in the photodiodes.
In the CMOS sensor, for example, pixels are arranged in a tow-dimensional matrix on a light-receiving surface, and a photodiode is disposed on the pixel basis. Signal charges generated and stored in each photodiode during reception of light are transferred to a floating diffusion by driving a CMOS circuit, and the signal charges are converted to signal voltages so as to be read.
In the CCD element, for example, pixels are arranged in a tow-dimensional matrix on a light-receiving surface, and a photodiode is disposed on the pixel basis, as in the CMOS sensor. Signal charges generated and stored in each photodiode during reception of light are transferred through a CCD vertical transfer line and a horizontal transfer line so as to be read.
In the above-described solid-state image pickup device, e.g., a CMOS sensor, for example, the above-described photodiodes are disposed on a surface of a semiconductor substrate. An insulating film of, for example, silicon oxide, is disposed as a layer covering the photodiodes. Wiring layers are disposed in the insulating film except photodiode regions so as to avoid hindering the entrance of light into the photodiodes.
However, regarding the above-described solid-state image pickup device, the area of the light-receiving surface has been reduced as elements have been made finer. Accompanying this, a problem occurs in that the rate of incident light decreases and the sensitivity characteristics deteriorate.
A structure, in which light is condensed by using an on-chip lens, an interlayer lens, or the like, has been developed as a countermeasure against this. In particular, a solid-state image pickup device has been developed, in which an optical waveguide for guiding the light incident from the outside to a photodiode has been disposed in the insulating film above the photodiode.
Japanese Unexamined Patent Application Publication Nos. 2003-224249 and 2003-324189 disclose solid-state image pickup devices in which concave portions are disposed in insulating films above photodiodes, the concave portions are filled with silicon nitride that is a substance having a refractive index higher than the refractive index of silicon oxide (hereafter referred to as high-refractive index substance) and, thereby, optical waveguides for guiding the incident light to the photodiodes are disposed.
Japanese Unexamined Patent Application Publication No. 2004-207433 discloses a solid-state image pickup device in which a concave portion of an insulating film above a photodiode is filled with a silicon nitride film and a polyimide film and, thereby, an optical waveguide is disposed.
Japanese Unexamined Patent Application Publication No. 2006-190891 discloses a solid-state image pickup device in which an insulating film including a diffusion-preventing layer in the layer, a concave portion is disposed in a portion of the insulating film, the portion being above a photodiode, in such a way that the diffusion-preventing layer is removed, and the concave portion is filled with a silicon oxide film.
On the other hand, Japanese Unexamined Patent Application Publication No. 2006-222270 discloses a solid-state image pickup device, in which a concave portion of an insulating film above a photodiode is filled with a TiO-dispersion type polyimide resin and, thereby, an optical waveguide is disposed.